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Old 03-23-2020, 04:22 PM   #1
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What’s An Engine Smoke Test? * Who’s done it?

==> If you have done a smoke test on your engine, please share your experiences with the rest of us.

==> If you never heard of a smoke test, I can point you in the right direction to learn more about it; and after you watch a few videos you may even decide to make your own smoke machine!

It’s like they say: “What you don’t know can hurt you!”

…So do a smoke test and sleep better knowing your air delivery system & exhaust system don’t have leak; I.e., if you don’t see smoke, then there’s a good bet you don’t have any leaks.

Note: If your ISC-350 does not have 24” of boost, you might have a leak in your cold/warm air delivery system; or maybe the turbo hose is cracked.

Note: If your bedroom is warmer than you think it should be, after driving your RV, then you might have an exhaust leak. This happened to be, but Cummins said the exhaust gasket was the problem, and it only leaked when I accelerated. They wanted me to buy a new manifold (a $2,000 repair), but when I told them to just mill or belt sand the flange and put some new gaskets on… they balked, but did as I asked. That was 40,000 miles ago! …But I was grateful they found the leak. Note: It took 1 person driving and one person listening and feeling round the exhaust manifold to find it. And then my bedroom was not as hot.

BTW: Has anyone ever used a turbo blanket to cut down on the heat off the exhaust manifold and/or the turbo?

TEST #1) The hot-side smoke test: Based on applying smoke to your exhaust pipe – primarily used to find exhaust manifold cracks or leaks in the muffler and turbo down pipe. (This guy got a surprise!)


TEST #2) The cold-side smoke test: Based on testing everything on the compressor side of your turbo, Charge Air Cooler (CAC), and air delivery tubing leading to the engine intake manifold – primarily used to find cracks in the rubber boots and/or band clamps.

Note: A smoke test NOT the same performing a vacuum test for these reasons: A vacuum test will confirm there is or is not a leak in a “closed system”…like your air conditioning lines vs. the smoke test that will show you were the leak is in an “open system” …like your exhaust system and air delivery system. (It’s an open - somewhere due to the valves being open.)

==> I think it’s possible to make own smoke machine at home… for cheap! …And maybe some of you may think it’s even fun! For example: Maybe you can do this project with your grandson or granddaughter?

Just take a look at these videos for ideas on how to build your own smoke machine with a soldering iron, old sock, and some mineral oil. Then take a plastic soda bottle to use as a tailpipe “tube stopper” or invent your own. Have fun and good luck!

Video #1: How to use a smoke machine:

Video #2: How to use a professional smoke machine on your RV exhaust:


Video #3: How to build your own smoke machine: https://youtu.be/EhNQiIRsCCk

Please post your results! …And if you find a leak, please tell us how you fixed it?

For those of you who believe in the “right tool for the right job,” you might want to order some of these parts:

Smoke Kit (12V):

Smoke Kit (Air Compressor Style):

Automotive Cap Plug Kit: (1/8 to 4") $28

5" inflatable block off bladder ($36)

TURBO LEAK TESTER (Just for grins.)
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2004 Itasca "Horizon" 40AD, ISC-350HP Cummins with 100,000 miles... and the best of 3 Diesels I have owned thus far!
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Old 03-29-2020, 03:03 PM   #2
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Location: Orlando, Florida
Posts: 4,561
The problem with the majority of the smoke machines is that the output pressure is too low for any practical use on the diesel.

Sure it worked to find a large a crack in the exhaust manifold but with only 0.5 psi output pressure, it is not going to be useful to find leaks in a CAC (unless it's as big as that exhaust manifold crack in the video).

The CAC is typically tested by applying around 15 psi air pressure (and listening/feeling for the leak). I don't think you will find anything (like a loose clamp or small hole in the CAC) with only 1/2 psi pressure.

I would not spend $600 for that (Redline) tester - with the intent of using it for just diesel engine leak discovery.

The Autool tester in your amazon link says it goes up to 13 psi output pressure. That is the one you want if your testing CAC.
Mike ----- 2005 Beaver Patriot Thunder CAT C13 525HP, 42-ft Tag, with HydraLift
*SMC-Bvr-Mnco History/Chassis Info https://1drv.ms/f/s!AtvAXw_lfqbToxXYREK9YdBP08Jn
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